HALL Current Sensor DAQ 8-Layer Stackable HAT for Raspberry Pi
Eight HALL Current Sensor Data Acquisition; 1A to 300A Range; AC/DC, RMS; RS485/MODBUS; RTC, Watchdog.
Overview
Eight-layer stackable HAT for Raspberry Pi providing eight HALL effect current sensor inputs. Measures AC and DC current non-intrusively — no need to break the circuit — from 1A to 300A. Includes eight software-programmable LEDs, an RS485/MODBUS port, and a Real-Time Clock with battery backup for timestamped data logging.
- 8 HALL effect current sensor inputs — measures AC/DC current from 1A to 300A without breaking the circuit
- Eight software-programmable LEDs, triggerable at a pre-set input level
- Real-Time Clock with CR2032 battery backup for timestamped data logging
- Field-calibratable; RS485/MODBUS and hardware watchdog for standalone operation
- Eight-layer stackable; compatible with all Raspberry Pi versions from Zero to 5
Works with Open Automation Software
Compatible with widely used tools for control, monitoring, and system integration.
 |
 |
 |
 |
 |
INTERFACES AND I/O
| I/O's | Communication | Software Integration |
|---|---|---|
| • 8 HALL Effect Current Sensor Inputs | • I2C Port to Raspberry Pi | • Command Line |
| • Eight Software-Programmable LEDs | • RS485/MODBUS Port | • Python Library |
| • Real-Time Clock (CR2032 battery backup) | • Node-RED nodes | |
| • Arduino Library | ||
| • Home Assistant | ||
| Other Features | ||
| • Non-intrusive AC/DC current measurement via HALL effect sensors, 1A to 300A — no circuit interruption needed | ||
| • Field-calibratable; calibration data stored in non-volatile flash | ||
| • Hardware watchdog monitors Raspberry Pi and power-cycles on lockup | ||
| • TVS protection on all inputs | • Onboard resettable fuse (7A) | |
| • Wide input power: 5V or 12–24VDC — also powers the Raspberry Pi (4A continuous, 5A peak) | • 32-bit processor running at 64MHz | |
| • Pluggable connectors, 26–16 AWG wires | • Eight-layer stackable — up to 64 current channels per Raspberry Pi | |
DESCRIPTION
The HALL Current Sensor DAQ HAT provides eight non-intrusive current measurement channels for Raspberry Pi. HALL effect sensors measure AC and DC current from 1A to 300A without any need to break the circuit. A Real-Time Clock with CR2032 battery backup keeps accurate time through power failures, enabling timestamped data logging for energy monitoring and fault analysis.
Eight channels measuring AC or DC current from 1A to 300A non-intrusively via HALL effect sensors. No need to break the circuit — place the sensor around the conductor. Two supported input ranges, 2.5±0.625V and 2.5V±1V, provide flexibility for different measurement scales.
Eight onboard LEDs, one per channel, can be programmed to trigger at a pre-set level of the corresponding current input — useful for at-a-glance status monitoring without a connected display.
An onboard RTC with CR2032 coin-cell battery backup maintains accurate time even when power is removed. Enables accurate timestamping of measurement records for energy logging, fault detection, and scheduled control tasks.
The RS485 port can operate as a passive bridge for the Raspberry Pi or as a MODBUS RTU slave — any PLC, SCADA, or HMI can read all current values with no Pi required. Stack level is set by the ID0, ID1, ID2 DIP switches.
The onboard hardware watchdog monitors the Raspberry Pi and power-cycles it if the application fails to send a reset command within the configured timeout. Ensures continuous unattended operation in remote installations.
Each channel supports two-point field calibration to improve measurement accuracy. Calibration data is stored in onboard non-volatile flash and survives power cycles. The calibration procedure is documented in the User's Guide and GitHub repository.
TVS diodes on all inputs protect against ESD and transient spikes. An onboard 7A resettable fuse protects against accidental shorts.
Together with multiple add-on cards, the HALL Current Sensor DAQ HAT can be installed on a DIN-Rail for sturdy industrial installations.
TECHNICAL DETAILS
CARD LAYOUT
MECHANICAL SPECIFICATIONS
DIP SWITCH AND STACKING
The onboard 3-position DIP switch configures the stack address. Up to eight HALL Current Sensor DAQ HATs can be stacked on one Raspberry Pi; cards can be stacked in any order.
| Switch | Name | Function |
|---|---|---|
| ID0 | Stack ID bit 0 | Binary stack address bit 0 (LSB) — sets card level 0–7 |
| ID1 | Stack ID bit 1 | Binary stack address bit 1 |
| ID2 | Stack ID bit 2 | Binary stack address bit 2 (MSB) |
ELECTRICAL SPECIFICATIONS
| Power | |
|---|---|
| Power supply | 3.5mm Pluggable Connector, 5V/5A or 12–24VDC |
| Power consumption | 50mA |
| Onboard resettable fuse | 7A |
| HALL Current Inputs | |
|---|---|
| Number of channels | 8 |
| Measurement type | AC and DC current, 1A to 300A (non-intrusive, HALL effect) |
| Supported input ranges | 2.5 ± 0.625 V and 2.5 ± 1 V sensor output |
POWER REQUIREMENTS
Power supply: The card operates from either a 5V/5A or a 12–24VDC external power supply connected to its own pluggable power connector. When powered from 12–24VDC, the card supplies 5V and up to 4A continuous, 5A peak to the Raspberry Pi over the GPIO bus, eliminating the need for a separate Raspberry Pi power supply. A local 3.3V regulator powers the rest of the circuitry. Operating current is 50mA.
PLUGGABLE CONNECTORS
All I/Os connect to heavy-duty 3.5mm pitch pluggable screw terminal connectors rated at 8A, accepting wire gauges from 26 to 16 AWG. Connectors can be unplugged from the board for convenient field wiring and debugging without disturbing the rest of the installation.
COMMUNICATION INTERFACES
HARDWARE WATCHDOG
The onboard hardware watchdog monitors the Raspberry Pi. If the application fails to send a reset command within the configured timeout, the watchdog cuts power to the Pi and restores it after the configured off period. The watchdog is disabled at power-up and is activated automatically after the first reset command is received. Use 8crt -h to see all watchdog commands.
| Parameter | Value |
|---|---|
| Initial timeout period | Configurable — allows time for Raspberry Pi to boot and start the application |
| Running timeout period | Configurable — normal operating timeout |
| Off period | Configurable — duration the Raspberry Pi power is cut when timeout triggers |
| Reset counter | Stored in non-volatile flash; can be read or cleared at any time |
COMPATIBILITY
| Interface | I2C (addresses 0x19 to 0x20) |
| GPIO used | GPIO2 (SDA), GPIO3 (SCL) — 2 pins only; remaining 24 GPIO pins stay free |
| Onboard processor | 32-bit, running at 64MHz |
| Max stack | 8 cards — up to 64 current channels; different Sequent HATs can be freely mixed |
| Compatible with | All Raspberry Pi versions from Zero to 5 (40-pin GPIO header) |
FIRMWARE UPDATE
The onboard microcontroller firmware can be updated in the field. The update tool downloads the latest firmware from Sequent Microsystems' servers and flashes it to the board over I2C.
Running the Update
~$ cd ~/8crt-rpi/update/
~/8crt-rpi/update$ ./update <id>
Replace <id> with the board stack address (0-7). Full instructions including recovery procedures are available at:
https://github.com/SequentMicrosystems/8crt-rpi/tree/master/update
DOWNLOADS
| Schematics (PDF) | CAD | Software & Integrations |
|---|---|---|
| Schematic V1.0 | 3D STEP Model | Command Line |
| 3D Printing Enclosure | Python Library | |
| Node-RED nodes | ||
| Arduino Library | ||
| Home Assistant |
WHAT'S INCLUDED
When you purchase the card you will receive the following items:
| 1. HALL Current Sensor DAQ HAT for Raspberry Pi |
|---|
 |
| 2. Mounting Hardware | |
|---|---|
 |
|
| 3. Connector Plugs for all Inputs | |
|---|---|
 |
|
QUICK START
- Plug your card on top of your Raspberry Pi and power up the system.
- Enable I2C communication on Raspberry Pi using
raspi-config. - Install the software from GitHub:
~$ git clone https://github.com/SequentMicrosystems/8crt-rpi.git~$ cd 8crt-rpi~/8crt-rpi$ sudo make install~/8crt-rpi$ 8crt -h
The program will respond with a list of available commands. To read more about the CLI, please refer to the README file. If you would rather use a different platform, you can access the same functionality through dedicated, ready-to-use integrations in the Downloads tab above.
Expand Your System
-
In stockEight Relays 4A/120V 8-Layer Stackable HAT for Raspberry Pi
Eight Relays 4A/120VAC, 24VDC N.O./N.C. contacts and LED indicators; RS485 Port. -
In stockRTD Data Acquisition 8-Layer Stackable HAT for Raspberry Pi
Eight Channel RTD Data Aquisition HAT; 0.01% accuracy through calibration; PT100/1000 Sensors; RS485/MODBUS, Watchdog. -
In stockSixteen LV Digital Inputs 8-Layer Stackable HAT for Raspberry Pi
Sixteen 3V-24V Opto-isolated Inputs with LED indicators; RS485/MODBUS, Hardware Watchdog. -
In stockSmart Fan HAT the Best Cooling Solution for Raspberry Pi
PWM controlled 40x40x10mm Fan keeps Raspberry Pi temperature constant; Stackable with any other HAT.
